package com.test.daily.leetcode.y2022.m05.day0518.v09;

import java.util.Stack;

/**
 * @author Tom on 2022/5/18
 */
public class Solution {
    public static class Node {
        int value;
        Node next;

        public Node(int value) {
            this.value = value;
        }
    }

    public static boolean isP1(Node head) {
        if (head == null) return true;
        Stack<Node> stack = new Stack<>();
        Node cur = head;
        while (cur != null) {
            stack.push(cur);
            cur = cur.next;
        }
        cur = head;
        while (stack.isEmpty()) {
            if (stack.pop().value != cur.value) {
                return false;
            }
            cur = cur.next;
        }
        return true;
    }
    public static boolean isP2(Node head){
        if(head == null||head.next == null){
            return true;
        }
        Node cur = head;
        Node right = head.next;
        while(cur.next != null || cur.next.next != null){
            right = right.next;
            cur = cur.next.next;
        }
        Stack<Node> stack = new Stack<>();
        while(right != null){
            stack.push(right);
            right = right.next;
        }
        cur = head;
        while(!stack.isEmpty()){
            if(stack.pop().value != cur.value){
                return false;
            }
            cur =cur.next;
        }
        return true;
    }
    public static boolean isP3(Node head){
        if(head == null || head.next == null){
            return true;
        }
        Node n1 = head;
        Node n2 = head;
        while(n2.next != null || n2.next.next != null){
            n1 = n1.next;
            n2 = n2.next.next;
        }

        n2 = n1.next;
        n1.next = null;
        Node n3 = null;
        while(n2 != null){
            n3 = n2.next;
            n2.next = n1;
            n1 = n2;
            n2 = n3;
        }
        // n1 為最後一個節點,需要保存
        n3 = n1;
        n2 = head;
        boolean ans = true;
        while(n2 != null && n1 != null){
            if(n2.value != n1.value){
                ans = false;
                break;
            }
            n1 = n1.next;
            n2 = n2.next;
        }
        n1 = n3.next;
        n3.next = null;
        while(n1 != null){
            n2 = n1.next;
            n1.next = n3;
            n3 = n1;
            n1 = n2;
        }
        return ans;
    }
}
